With Industrialization and Assimilation: Understanding Ethnic Change in the Modern World, Elliott D. Green contributes one of the most important recent additions to the canon of grand theories of ethnic politics and nationalism. Nimbly integrating ambitious statistical analysis of global patterns with individual life stories from specific countries, this multi-method study makes a powerful case that ethnic change is natural and that it commonly follows material incentives. And the most powerful material nation-making incentives of all, Green argues, have historically come from processes of industrialization.

Literatures on ethnicity and nationalism have traditionally structured themselves around two rival theoretical perspectives. Primordialists see ethnic groups and nations as tending to be age-old, natural, unchanging, singular within any one individual, and fraught with conflictual and emotive potential. Constructivists see them as changeable, modern (even recent) creations that involve multiple identities whose salience can vary dramatically from situation to situation. Actual primordialism is so discredited, however, that hardly any self-respecting social scientist calls themselves a primordialist anymore, making the scholarly debate rather one-sided. At the same time, in framing their arguments against primordialism, constructivists like Green these days are not arguing against a strawman. Instead, they are objecting to the persistent insinuation of primordialist assumptions in many academic analyses, as still happens when large-N statistical studies treat ethnic groups as exogenous independent variables in their analyses. So primordialism lives on not as a well-articulated theory but as an uncritically adopted assumption.

Green’s book, at its core, aims to destroy this assumption once and for all. It is replete with compelling evidence not only that altered circumstances and incentives routinely produce changes in individuals’ identities, but that such processes, when taken on aggregate, can dramatically shift the whole ethnic structure of a country—and do so well within the time frame of a single generation. Examining censuses over time thus often reveals major and rapid shifts in national-level ethnic composition that cannot be accounted for by migration patterns or natural sources of population change. Singling out the widely used Ethno-Linguistic Fractionalization (ELF) index to make the point, Green powerfully demonstrates that its content has frequently been shifted by variables it is sometimes used to “explain.”

Beyond this major point, however, Green is also taking on many other constructivists. He does so by reviving and developing one of its most pedigreed—but increasingly abandoned—arguments: That industrialization lies at the heart of the kind of ethnic change associated with the development both of modern nations and of ethnic minority subnationalisms that challenge them. As he notes in the book, constructivist perspectives have in recent decades come to emphasize other factors as the great identity constructors in history, including political institutions, state nation-building policies, and media markets. In emphasizing the importance of industrialization, though, Green is explicitly rejecting a long history of modernization theory, discredited for its teleological and Eurocentric assumptions. What he rescues from it, however, is a core argument that processes of economic change bring social change, and more specifically that the development of the industrial economy can powerfully shape ethnic and national identity. But Green passes no normative judgements and assumes no historical endpoint, demonstrating that industrialization’s effects on identity can be reversed by deindustrialization or developments that otherwise weaken the incentives people have to cast their families’ material lot with nationwide industrialized economies.

The heart of Green’s argument is the insight that industrialization tends to promote assimilation into the state’s core ethnic group. He argues this happens not (as scholars like Erenst Gellner have supposed) primarily through state-led processes designed to facilitate industrialization like education and the advent of literacy, but instead through grassroots choices involving material calculations. Industrialization reduces the value of narrower, lower-level ethnic identities linked to rural life while making it advantageous for individuals to become more seamlessly integrated into identities and cultures linked to new opportunities in (usually) urban centers. The result is the appearance of strong national identities, with minority-group challenges arising primarily from uneven industrialization. He goes even further, arguing that state efforts to “build nations” typically fail unless they are undergirded by robust industrialization, and that the latter can build nations by itself even when the state is inattentive or even opposed to the process.

Green makes his case through an ambitious empirical strategy of global, world-historical scope. After developing the core tenets of his argument in the first two chapters, an introduction and a discussion of theory and measures, Green begins supporting his argument by going back to the ancients. Chapter 3 thus opens with a brief discussion of how the premodern economies of ancient Greece and the Roman empire meant that identity was generally very fragmented, with certain proto-industrial developments producing senses of national identity that tended, at best, to be “limited and often temporary” (46). The chapter then turns to Europe, “where industrialization proceeded most rapidly in the nineteenth century” (51), making a case that uneven patterns in this process account for the appearance of strong unifying nationalisms in some areas rather than others. A case study of South Africa during the same period argues industrialization thwarted “efforts by the white elite to disrupt broader identity formation among black South Africans,” facilitating the victory of Nelson Mandela and his people. Chapter 4 then presents quantitative evidence that industrialization tends to reduce ethnolinguistic fractionalization (promote identification with broader national identities) worldwide. Change in carbon emissions between 1961-85, he shows, is a strong predictor of change in “the percentage of people identifying with the largest ethnic group in the country” (74) during the same period.

Subsequent chapters take readers to Türkiye (Chapter 5), Sub-Saharan Africa (Chapters 6–7), the United States (Chapter 8), and New Zealand (Chapter 9). Each of these chapters allows Green to shore up his argument in a particular way. In Türkiye, he uniquely finds data available that enable him to test his argument in granular detail, pinpointing that Turkish nation-building’s successes (and failures, as with the Kurds) owed much more to patterns of industrialization than to government policies. In Africa, he argues low levels of industrialization underlie the high degrees of ethnic diversity there, but shows that exceptions like Botswana prove the rule. And looking at indigenous peoples in societies conquered by Anglophone settlers, he demonstrates not only that industrialization initially promoted unified “indigenous people” identities despite frequent government efforts to prevent them but also that native American casino legalization and fishing policies empowering New Zealand Māori tribes reversed this process precisely by raising the relative material value of tribal identities.

As with any relatively short book making a grand argument, readers will come away with questions. One is the extent to which the phenomenon Green explains is actually ethnic change. The book addresses what it calls vertical ethnic change, which refers to shifts in the relative salience of narrower and broader identities (e.g., Cherokee and Native American) and is distinct from horizontal change, which involves the actual crossing of a boundary distinguishing between one group and another (e.g., a Cherokee shedding this identity and reidentifying as Navajo or White). The change Green documents lies in whether people choose the broader or narrower category when asked their identity in a census or survey, or in whether they see one or the other as more relevant for their lives. But might this not simply reflect the situationality inherent in the multidimensionality that constructivists have long established is essential to identity, reflecting more the dynamic work that identity does for people rather than a change in a person’s ethnic identity itself? Other readers might wonder who determines whether change is horizontal or vertical. Groups do not always agree on which identities are subcategories of which. For example, to hear Russia’s Vladimir Putin talk, “Ukrainian” is a subcategory of “Russian,” but anyone listening to Ukrainians themselves will be clear they see the distinction between Ukrainian and Russian as very much horizontal. Similar questions could be put to the book’s treatment of Kurds and Turks in Türkiye. By helping foreground such questions, though, the book has provided an important spur to the field to deepen our investigation into the foundations of ethnicity and identity more generally.

Overall, Industrialization and Assimilation is a highly satisfying read, written in a manner that should be accessible to advanced undergraduates and of broad appeal to anyone interested in ethnic politics, political economy, or even world history more broadly. It is sure to be a landmark in the field for a long time to come.